Asynchronous Transfer Mode ("ATM") is a networking protocol designed to support high speed digital voice and data communications. It is generally believed that within the next several years, most of the voice and data traffic generated throughout the world will be transmitted by ATM technology. Broadband packet networks based on ATM technology are enabling the integration of traffic having a wide range of characteristics within a single communications network. In order to be accepted by potential end users and communication network providers, these ATM based broadband networks must meet certain performance requirements.
In general, an ATM bearer service, e.g., the broadband network, provides a sequence-preserving, connection-oriented cell transfer service between a source and destination with an agreed upon Quality of Service ("QoS") and throughput. That is, the underlying layers of the ATM protocol should provide the convergence and transmission functions that would preserve the traffic shape and QoS of the traffic as the ATM cells are passed between the ATM layer and the underlying layers. Although the prior art discusses in great detail how these convergence and transmission functions are supported on a point-to-point medium, e.g., 155.52 Mbps on Synchronous Optical Network ("SONET"), 52 Mbps on Unshielded Twisted Pair ("UTP"), and 155 Mbps on fiber optic networks, etc., the prior art does not discuss how these same functions can be supported on multiple access networks.
In point-to-point medium systems, at connection set-up time, an end-user device negotiates with the network, at the network layer, certain QoS parameters, e.g., Cell Delay Variation ("CDV"), Cell Loss Priority ("CLP"), etc., and traffic descriptors according to the types of connection, e.g., circuit emulation, real-time video and audio, connection-oriented data transfer, connectionless data transfer, etc. Assuming a point-to-point connection at the User-Network Interface ("UNI"), the insertion of a cell for a particular connection is scheduled by the ATM layer and hence can be done completely under the control of the end-user device, following the negotiated contract with the network.
However, if the end-user device is attached to a multiple access network, such as a Hybrid Fiber/Coaxial network ("HFC") or a Switched Digital Video ("SDV") network, where multiple end-user devices access shared bandwidth, the traffic shape and QoS parameters may be temporally distorted at the insertion time as a result of bandwidth contention on the access network. Accordingly, there is a need to provide a simple and effective method which mitigates the effect of bandwidth contention on the shape of traffic and QoS parameters.